C# 線程資源同步方式總結（五）——Mutex 跨進程同步與 ReaderWriterLock 讀寫分離

5. Mutex：跨進程互斥體

特點：命名互斥體可跨進程/機器同步，無 Wait/Pulse 機制。

雙進程測試代碼

static void Main(string[] args)
{
    Mutex configFileMutex = new Mutex(false, "configFileMutex");
    Console.WriteLine("Wait for configFileMutex Process Id: " + Process.GetCurrentProcess().Id);
    configFileMutex.WaitOne();
    Console.WriteLine("Enter configFileMutex Process Id: " + Process.GetCurrentProcess().Id);
    Thread.Sleep(10000);
    
    if (!File.Exists(@".config.txt"))
    {
        FileStream fs = File.Create(@".config.txt");
        StreamWriter sw = new StreamWriter(fs);
        sw.WriteLine("This is a Test!");
        sw.Close(); fs.Close();
    }
    else
    {
        string[] lines = File.ReadAllLines(@".config.txt");
        foreach (string line in lines) Console.WriteLine(line);
    }
    configFileMutex.ReleaseMutex();
    configFileMutex.Close();
}

執行結果驗證

第二進程阻塞於 WaitOne，第一進程寫入釋放後，第二進程獲得互斥體讀取內容。

6. ReaderWriterLock：多讀單寫

場景：頻繁讀取、偶爾寫入。讀取共享、寫入獨佔。

代碼示範

private static ReaderWriterLock m_rwl = new ReaderWriterLock();
private static int m_int = 0;

private static void Read()
{
    while (true)
    {
        Console.WriteLine(Thread.CurrentThread.Name + " AcquireReaderLock");
        m_rwl.AcquireReaderLock(10000);
        Console.WriteLine("Thread: {0} Value: {1}", Thread.CurrentThread.Name, m_int);
        m_rwl.ReleaseReaderLock();
    }
}

private static void Writer()
{
    while (true)
    {
        Console.WriteLine(Thread.CurrentThread.Name + " AcquireWriterLock");
        m_rwl.AcquireWriterLock(1000);
        Interlocked.Increment(ref m_int);
        Thread.Sleep(5000);
        m_rwl.ReleaseWriterLock();
        Console.WriteLine(Thread.CurrentThread.Name + " ReleaseWriterLock");
    }
}

執行輸出分析

• 寫入執行緒持有 WriterLock 時，所有讀取執行緒阻塞
• 釋放 WriterLock 後，多個讀取執行緒同時獲得 ReaderLock (交錯輸出證明)
• 無寫入時，多讀取並行無阻塞